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Study on the Functional Components and Antioxidant Capacities of Young Fruits of Citrus

Author: JiangPing
Tutor: YeXingQian
School: Zhejiang University
Course: Of Food Science
Keywords: Young fruits of citrus functional components Antioxidant capacity Freeze-drying Hot air drying Sun-drying
CLC: S666
Type: Master's thesis
Year: 2008
Downloads: 78
Quote: 4
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Abstract


Young fruits of citrus were raw materials of Chinese traditional medicine ~ Fructus Aurantii Immaturus all the while, which was processed generally by sun drying after collecting from orchard. But the studies on its functional components were not comprehensive and the effect of drying process on the functional components and their antioxidant capacity were still unknown. In this dissertation major functional compounds in 16 varieties of young citrus fruits were analysed . And effect of different drying methods and different hot air drying temperature on the composition and antioxidant capacity were evaluated . The main results were presented as follows:(1) Young fruits of sixteen representative citrus varieties (nine mandarins, two sweet oranges, one sour orange, one lemon, one Huyou, one pummelo and one hybrid) from Zhejiang province were investigated mainly on the composing and contents of four flavanone glycosides (FGs), two polymethoxylated flavones, eight phenolic acids, limonin, nomilin and synephrine. The results showed that flavanone glycosides were abundant in young fruits of citrus. For example, the highest contents of hesperidin (261.63 mg/g DW) and naringin (67.5 mg/g DW) were present in young fruits of Citrus unshiu Marc. cv Owari and Citrus gradis×Citrus sinensis, respectively. The contents of polymethoxylated flavones in young fruits of citrus were relatively low. The highest contents of nobiletin (13.66 mg/g DW) and tangeretin (11.95 mg/g DW) were present in Zhuhong young fruits. In young fruits of citrus, the main phenolic acids were cinnamics acids. The content of limonin was higher than nomilin in most young fruits. The order of the contents of synephrine in different citrus varieties was that: mandarin > sweet orange > sour orange.(2) The antioxidant capacity of extract of young fruits of sixteen citrus varieties was evaluated by three kinds of in vitro antioxidant methods (FRAP, DPPH, ABTS). The results showed that the content of total phenolics in young fruits of Zhuhong citrus was the highest, and the antioxidant capacity of its extract was also the highest.(3) The correlations of the contents of functional compounds, total phenolics(GAE), FRAP (TEAC), DPPH (TEAC) and ABTS (TEAC) were analyzied. The results indicated that the correlation coefficients of the antioxidant capacity detected by three methods with total phenolics, total flavanoids content, total extractable phenolic acids were extremely significant (p<0.01).and the correlation coefficients of the three antioxidant methods with the same mechanism based on single electron transfer (SET) were also significant (p<0.01).(4) The effects of three different drying methods (freeze-drying, 60℃hot air drying, sun-drying) on young fruits of citrus on functional compounds and antioxidant capacity were investigated. Young fruits of Ponkan, Gaocheng, Foyou, Changshanhuyou were selected to be the raw materials. The results showed that: Effects of the three drying methods on contents of flavanoids, phenolic acids and synephrine were significant (p<0.05). The order of the contents was freeze-drying > 60℃hot air drying > sun-drying. Effects of three drying methods on contents of limonin and nomilin were not significant (p>0.05). The order of the contents of total phenolics was freeze-drying > 60℃hot air drying > sun-drying. The antioxidant results of FRAP and DPPH showed that freeze-drying > 60℃hot air drying > sun-drying. But the results of ABTS showed that the effects of three drying methods were not significant (p>0.05).(5) The effects of different hot air drying temperature (30℃、45℃、60℃、90℃and 120℃) on young fruits of citrus in terms of functional compounds and antioxidant capacity were investigated. Young fruits of Ponkan, Gaocheng, Foyou, Changshanhuyou were selected to be the raw materials. The results showed that: Effects of hot air drying temperature on contents of flavanoids, phenolic acids and synephrine were significant (p<0.05). And the highest contents of them were found in 60℃hot air drying samples, lower or higher temperature all led to the decrease of the contents. The lowest contents of them were present in 120℃hot air drying samples. But the effects of hot air drying temperature on contents of limonin and nomilin were not significant (p>0.05). The order of the contents of total phenolics and the antioxidant capacity of FRAP, DPPH and ABTS were: 120℃> 90℃> 60℃> 45 or 30℃(p<0.05).

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